Increasing rates of carbon burial in southwest Florida coastal wetlands

Coastal mangroves and marshes use photosynthesis to change carbon dioxide into plant material like leaves, wood, and roots. As these materials die over time, they don’t decompose the same way they might in a dry soil environment. Instead, daily ocean tides flood the soil, removing the oxygen, and allowing dead plant materials to be buried and preserved for hundreds to thousands of years or more. This “carbon burial” process is a global benefit because it means that carbon dioxide, a greenhouse gas, is stored belowground where it can no longer warm the atmosphere. Mangroves and marshes bury carbon more quickly than most other ecosystems, but little is known about how burial rates change over time. In this study, we quantify how rates of carbon burial have changed in southwest Florida coastal wetlands in the past century. We find that carbon burial is 2.5–4.5 times greater today than it was a century ago in mangroves, and 1.9 – 2.3 times greater in marshes. We propose sea‐level rise as the most likely cause of increased carbon burial. Rising seas provide the means and opportunity for wetlands to bury more carbon, but if sea level rises too quickly, these wetlands may drown.